1. Field of Invention
The present invention relates to the field of pressure sensors. More specifically, the present invention relates to a pressure sensor integrated onto a circuit substrate.
2. Description of the Related Art
Pressure sensors are known to those skilled in art. Typically, these devices fall into two categories. In the first category are set-point pressure sensors, more properly referred to as pressure switches, that actuate when a specified pressure is reached. The second category contains the more sophisticated pressure sensors that are capable of measuring the ambient pressure and reacting accordingly. Generally, pressure switches are less complex and more cost efficient than pressure sensors.
In low tire pressure warning systems, a typical mass-market application, the critical function of the warning system is to identify when the tire pressure falls below a specified value. Accordingly, using a pressure sensor with the ability to measure the tire pressure adds extra expense to the system.
FIG. 1 illustrates an exploded view of a conventional pressure switch. The conventional pressure switch includes a base member 11 having tabs 12 for securing the conventional pressure switch on a circuit board. Connected to the base member 11 is a metal enclosure 13. A hollow contact pin 14 passes through an opening in the base of the metal enclosure 13 and allows the pressure of and/or the gas within the pressure switch to be changed. A non-conductive end piece 15 serving as a diaphragm support is attached to the end of the contact pin 14 terminating within the metal enclosure 13. A thin metal diaphragm 17 covers the open end of the metal enclosure 13. A metal spring 16 biases the end piece 15 and the contact pin 14 against the diaphragm 17. The metal spring 16, in combination with the hollow contact pin 14, is selected to set the pressure at which the switch responds. A cover 18 having a small, central through opening 19 provides protection for the diaphragm 17.